1. Field of the Invention
The present invention generally relates to the art of electrical energy storage devices and more particularly, to an electrode of an electrochemical cell or capacitor produced by a physical vapor deposition process.
2. Prior Art
Physical vapor plating involves introducing a material of interest into a vacuum and heating it to a temperature at which the material reaches its vapor pressure. When molecular rays of the vaporized material attain a sufficient energy such that their mean free path causes them to impinge upon and precipitate onto a substrate, a coating of the material is formed. While physical vapor deposition processes are known in the art, as of yet, they have not been used to deposit an electrode active material onto a substrate to provide an electrode component for an electrochemical cell and to deposit a semiconductive or pseudocapacitive material onto a substrate to provide an electrode component for a capacitor.
The present invention is directed to a novel and unique application of the physical vapor deposition process. The present process provides a coating of an electrochemically active material on a substrate, preferably a conductive substrate. The thusly produced coated substrate is useful as an electrode, for example, a cathode electrode incorporated into a primary electrochemical cell, and as the anode and/or the cathode of a secondary electrochemical cell. The assembly of the cell incorporating the electrode component made by physical vapor depositing an electrode active material onto a conductive substrate according to the present invention is preferably in the form of a wound element cell. That is, the fabricated cathode together with an anode and a separator are wound together in a xe2x80x9cjellyrollxe2x80x9d end type configuration or a xe2x80x9cwound element cell stackxe2x80x9d such that the anode is on the outside of the roll to make electrical contact with the cell case in a case-negative configuration. Other types of cells such as prismatic, bobbin shape and flat cells are also possible with the present invention.
In the case of a capacitor, the present physical vapor deposition process is useful for producing an anode or a cathode in an electrochemical capacitor or the cathode in an electrolytic capacitor. Regardless the type, the capacitor configuration generally includes a substrate of a conductive metal such as titanium or tantalum provided with a semiconductive or a pseudocapacitive oxide coating, nitride coating, carbon nitride coating, or carbide coating.